Imagery released September 9 by the NASA/Jet Propulsion Laboratory in Pasadena, California show the two moons of Mars - Phobos and Deimos cutting across the martian night sky. The unique pictures come courtesy of the Spirit robot, using its onboard camera system to take longing looks at the parade of celestial objects as they flew overhead.

An animation has been produced showing both martian moons: Deimos on the left and Phobos on the right - as they travel across the night sky in front of the constellation Sagittarius. Part of Sagittarius resembles an upside-down teapot. Phobos is the brighter object on the right; Deimos is on the left.

Spirit acquired the enhanced-brightness images with its panoramic camera on the night of August 26, 2005.

According to Jim Bell of Cornell University in Ithaca, New York, by collecting images of the two moons scientists can better chart their orbital positions and learn more about the composition of the Mars-orbiting bodies. Bell is lead scientist for the panoramic cameras on both the Spirit and Opportunity Mars rovers now scouting about on the red planet.

Also released is a sequence of images of Mars' largest moon, Phobos.

The first two images in the sequence show gradual enhancements in the surface detail of Phobos, made possible through a combination technique known as "stacking."

This procedure uses a mathematical process known as "Laplacian sharpening" to reinforce features that appear consistently in repetitive images and minimize features that show up only intermittently.

In the image sequence, the large crater named Stickney is just out of sight on the upper right limb of Phobos.

In the Phobos image sequence, Spirit acquired the first two images with the panoramic camera on the night of August 26, 2005. The far right image of Phobos, for comparison, was taken by the High Resolution Stereo Camera on Mars Express, a European Space Agency orbiter.

The third image in the sequence was derived from the far right image by making it blurrier for comparison with the panoramic camera images to the left.

Another use of this nighttime imagery is to look for the presence of nighttime clouds or haze.

The ability of Spirit to become a nighttime skywatcher on Mars is the rover's extra solar energy collected during the day.